Stark Eran, Drori Rotem, Abeles Moshe
Department of Physiology, Hadassah Medical School, Hebrew University, Jerusalem, Israel.
Cortex. 2009 Mar;45(3):418-31. doi: 10.1016/j.cortex.2008.03.011. Epub 2008 Jul 10.
While it is generally accepted that multiple neurons cooperate to generate movement, the precise mechanisms are largely unknown. One way to generate a robust local control signal is for nearby neurons to share similar properties. To study this possibility, we recorded neural activity from the macaque motor cortex during two drawing tasks: free scribbling, and tracing given paths. We analyzed neural activity in relation to three kinematic parameters - position, velocity, and acceleration - while explicitly considering temporal correlations between them. Single-unit (SU) activity was typically related to one parameter, most often velocity, and tended to precede movement. Different SUs encoded different parameters, but nearby units tended to prefer the same parameter. Moreover, while SUs covered a wide range of positions, velocity directions, and acceleration directions, SUs recorded by the same electrode tended to prefer similar values of the same parameter. Nevertheless, some nearby units exhibited marked differences. Multi-unit activity (MUA), estimating the spiking activity of many neurons around the recording electrode, also tended to be related to one parameter and precede movement. However, overall correlations between MUA and movement were more than twice as strong as SU correlations. Finally, SUs and MUAs recorded by the same electrode tended to share similar properties. These two lines of evidence converge to suggest that activity of motor cortex neurons within approximately 200 micrometers is accumulated in a manner useful for representing a single parameter. However, even within a small region there are also neurons related to other parameters, potentially facilitating coordination between distinct parameters.
虽然人们普遍认为多个神经元协同作用以产生运动，但其精确机制在很大程度上仍不清楚。产生强大局部控制信号的一种方式是让附近的神经元具有相似的特性。为了研究这种可能性，我们在两项绘图任务期间记录了猕猴运动皮层的神经活动：自由涂鸦和沿着给定路径追踪。我们分析了与三个运动学参数——位置、速度和加速度——相关的神经活动，同时明确考虑了它们之间的时间相关性。单神经元（SU）活动通常与一个参数相关，最常见的是速度，并且往往先于运动出现。不同的单神经元编码不同的参数，但附近的神经元倾向于偏好相同的参数。此外，虽然单神经元覆盖了广泛的位置、速度方向和加速度方向，但同一电极记录的单神经元倾向于偏好相同参数的相似值。然而，一些相邻的神经元表现出明显的差异。多神经元活动（MUA）估计记录电极周围许多神经元的放电活动，也倾向于与一个参数相关并先于运动出现。然而，多神经元活动与运动之间的总体相关性比单神经元相关性强两倍多。最后，同一电极记录的单神经元和多神经元活动倾向于具有相似的特性。这两条证据线共同表明，大约200微米范围内的运动皮层神经元活动以一种有助于表示单个参数的方式积累。然而，即使在一个小区域内，也存在与其他参数相关的神经元，这可能有助于不同参数之间的协调。
